Update: For the most part, KMM is living her best life!
We are having some issues with her not being friendly to the other cat (grandparent's cat next to us), so are doing our best to keep them separated and having them on different outside schedules.
One thing we noticed: Her breathing the last couple of days has been VERY fast. In fact, early this morning I was surprised and thought she was maybe getting ready to huck a hair-ball.
... but she just continues to breath fast. It's not especially hot, and she's not exhibiting any other problems, so we called the vet. They said "keep an eye on her for if it gets worse or changes."
... so that's what we're doing for now.
Here's a video from this morning:
With that breathing I would at least get bloodwork and a couple chest x-rays done.
You are right. Much like chickens cats are masters at hiding illness.
